1. Field of the Invention
The invention relates to a metal racket, more particularly to a metal racket having a wider ball striking area compared to a racket with a looped head portion of the same size outer periphery and a frame having an oblongated cross-section to permit better ball control.
2. Description of the Related Art
There are two types of metal rackets presently available. The looped head portion (1) of a first type of conventional metal racket is shown in FIG. 1 to be made of an extruded metal tube having a cross-section that includes a pair of substantially triangular loop portions (2) and a flat connecting portion (3) bridging the loop portions (2). String holes are punched in the connecting portion (3) before the metal tube is bent so as to form the looped head portion (1). The manufacturing cost of the above described metal racket is relatively low because of the simple machining steps involved.
Although the above disclosed metal racket is low cost and is easy to construct, it has the following disadvantages:
(a) Unsightly peripheral grooves (4, 5) are formed on two sides of the connecting portion (3). The market value of the metal racket is thus affected because of the appearance of "inferior quality."
(b) The metal racket is less durable. Referring to FIG. 2, the connecting portion (3) curves inwardly when the striking impact of a ball is relatively strong. This results in poor ball control and in the eventual deformation of the metal racket.
Referring to FIG. 3, the looped head portion (6) of a second type of conventional metal racket is made of an extruded metal tube which has a substantially oblongated cross-section. The looped head portion (6) has a convex inner periphery (61) and a convex outer periphery opposite to the convex inner periphery (62). Since the looped head portion (6) does not have unsightly peripheral grooves similar to those of the looped head portion (1), the metal racket is therefore more durable and has a "high quality" appearance. The looped head portion (6) is further provided with a pair of spaced reinforcing ribs (7) which bridge the inner and outer peripheries (61, 62). The ribs (7) enhance the durability of the metal racket.
Because the cross-section of the looped head portion (6) is wider than that of the looped head portion (1), the ball striking area defined by the looped head portion (6) is correspondingly smaller. Referring to FIG. 4, a string web (8) of longitudinal and transverse string lines is held by the looped head portion (6). The longitudinal string lines are normally longer than the transverse string lines. The direction of ball rebound generally depends upon the striking point of the ball on the string web (8). It is easy to predict the direction of ball rebound when the ball strikes a point (Pl) on the string web (8), the point (Pl) being the center of symmetry of the looped head portion (6). The ball will generally be rebounded in a direction perpendicular to the string web (8) without any angular deviation when it strikes the string web (8) at the point (Pl).
The direction of ball rebound becomes more difficult to predict when the ball impacts points farther from the center of symmetry (Pl). This is because both the longitudinal and transverse string lines are bisected into segments of unequal length, thus causing the string lines to deflect at different angles with respect to the string web (8).
Referring to FIGS. 4, 5A and 5B, the impact points (P2) and (P3) are on different longitudinal lines (AA) and (BB) but are on the same transverse line (CC). The line (BB) is longer than the line (AA) and thus the line (AP2) is shorter than the line (BP3). The deflection angle (.THETA.2) of a ball rebounded from the longer string line (BB) is therefore smaller than the deflection angle (.THETA.1) of a ball rebounded from the shorter string line (AA).
Referring to FIGS. 4, 5C and 5D, the impact points (P2) and (P4) are on different transverse lines (CC) and (DD) but are on the same longitudinal line (AA). The line (DD) is longer than the line (CC) and thus the line (CP2) is shorter than the line (DP4). The deflection angle (.THETA.4) of a ball rebounded from the longer line (DD) is therefore smaller than the deflection angle (.THETA.3) of a ball rebounded from the shorter line (CC).
In view of the foregoing discussion, it can be concluded that the deflection angle of the ball is smaller when the string line is longer. In order to achieve better ball control, it is desirable to minimize the deflection angles of the string lines. To this end, it is necessary to lengthen the string lines and correspondingly increase the ball striking area.